This invention relates to turbine flowmeters and, more particularly, to overspeed protection for a turbine flowmeter.
A turbine flowmeter has a rotatable turbine wheel positioned to intercept fluid flowing through a line. The turbine wheel rotates at a speed proportional to the fluid velocity. The rotation of the turbine wheel is sensed by a pickup coil, which provides pulses to actuate an indicator.
One class of turbine flowmeter is designed for insertion in a fluid flow line as a probe. Such a probe is generally designed to disturb fluid flow as little as possible. As a result, the turbine wheel is small and is usually supported for rotation by fragile ball bearings. Rotation of the turbine wheel at a speed above that for which the flowmeter is designed may damage the fragile ball bearings.